Control device



Feb. 16, 19.54 WALKER 2,669,245

CONTROL DEVICE Filed June 6, 1945 Fig.l.

s 7 IA 8 I 5 y 9 no Eco i E g 4- g ca ll I QLQQJT GI g QA 6 4IA I I I I; M y 6AE Inventor A! lorne 13 Patented Feb. 16, 1954 CONTROL DEVICE Daniel Norman Walker, Ashby Parva, near Rugby, England, assignor to Power Jets (Research and Development) Limited, London, England, a

British company Application June 6, 1945, Serial No. 597,810

The invention relates to a valve device for certain control purposes. It seeks to provide a pressure-controlled valve which may have various applications but which is primarily intended to be sensitive to changes in a relatively low pressure, such as changes in atmospheric pressure whilst controlling a relatively high pressure, say in the order of tens or even hundreds of atmospheres. The invention more especially though not exclusively, seeks to provide apparatus for the control of pressure fuel supply to engines and especially aero-engines-which have characteristics such that for a given performance the fuel consumption must be varied in a relationship with ambient air pressure.

. There are at present being developed, aeroengines comprising in essence a compressor in the output of which combustion of liquid fuel is arranged for, and a gas turbine driving the compressor; the exhaust gas from which may constitute a propulsion jet. Such engines are self-adjusting as regards mixture strength when running stably. Their fuel consumption for a given speed in R. P. M. varies greatly with the ambient atmospheric pressure. For example, in one case, at a certain speed an engine will use about 1700 lbs. of hydrocarbon fuel per hour in standard atmosphere, sea level conditions, and only 300 lbs. per hour at a certain operational altitude. If the fuel supp-1y were maintained at a constant rate, it follows that the engine speed would progressively increase with altitude. There are, of course, certain safety limits to permissible speed. Therefore it is desirable that some expedient be adopted to cut down the fuel supply as height is increased. It is not regarded as practicable to do this manually, and even if it is done manually, the phenomenon results that a throttle range of movement which may be reasonable and adequate at sea-level is progressively diminished as altitude increases, with obvious disadvantages. It is an object of the invention to afford means for adjusting the fuel supply automatically with variations of altitude.

Itshould perhaps be added that present practice with engines of the kind stated, is to provide a fuel pump of a positive type driven directlyv by the engine and operating in a comparatively high pressure range, say 30-450 lbs. per sq. in.; some of the output from this pump is allowed to return to the fuel source through a relief valve, which valve controls the operative fuel pressure. Such a valve obviously has to pass back to source a quantity of fuel which increases pro rats. with altitude, and an uneconomical amount of Work done by the pump is thus wasted. 'A secondary 3 Claims. (Cl. 137-81) advantage sought by the invention is to minimise this Waste and incidentally to avoid unnecessary heating of the fuel.

The invention consists broadly in such a device, comprising a resiliently loaded relief valve controlling the pressure of the first fluid (i. e., that fluid which is to be controlled) the resilient load of which is variable by variation of the effective fluid pressure of a third fluid and means controlled by variations of pressure of the second fluid to vary the resilient loading on the relief valve by varying the effective fluid pressure of the third fluid. Thus in the case of the aero engine indicated, the first fluid is the actual liquid fuel being supplied to the engine, and the second fluid is the atmosphere, the pressure of which either by itself or as affected by pitot head due to forward speed, is regarded as the ambient pressure and acts upon the device. The third fluid is conveniently servo fluid, for example, lubricating oil, or some of the pumped fuel diverted and pressure controlled so as to be usable as a servo fluid.

Somewhat more specifically the invention comprises a valve device for controlling the pressure of a first fluid in accordance with variations in pressure of a second fluid, comprising a resiliently loaded relief valve controlling the pressure of the first fluid, a second valve set by variations of pressure of the second fluid, and a fluid pressure system such that changes of setting of the second valve permit more or less pressure from a servo source of pressure fluid to be applied so as to vary the resilient load on the relief valve. Preferably there is provided also means whereby the changes of resilient loading on the relief valve involve movement of an appropriate part, which movement is transmitted to an element of the servo valve so as to affect its setting, whereby a follow-up effect is achieved in the device. Further and more constructional features of the invention will become apparent from the following description of an example in which a valve device comprises a relief valve for the controlled pressure, a spring or spring-pack loading the relief valve, a servo, a servo piston or an equivalent such as a diaphragm moveable to vary the spring load under the influence of servo-fluid pressure, a servo-valve controlling the servo fluid pressure on the servo piston, and a barometric capsule or equivalent pressure-sensitive device susceptible to the controlling pressure (e. g., atmosphere) for its deflections and setting the servo valve by such deflections and mechanical action between the servo piston and servo valve,

. wherebyithis'valve is also settable in accordance device according to the invention, as applied in a gas turbine aircraft fuel system.

In Figure l, A represents a relief valve, loaded by a compression spring B the compressive stress in which is determined by servo fluid pressure acting in chamber C on top of servo piston D. The servo fluid is admitted to chamber C from a connection E, when the servo valve F ismoved' downwards, and is released for egress. through.

an escape connection G when the valve F is moved upwards. The valve F is moved by the deflections of a pressure-sensitive capsule (of the aneroid barometer kind)- the overall length or which is changed by pressure-caused deflections. The bottom of the caspule His held bya rod J which is mechanically movable, through arocker K and pushrod L in accordance with movement's of pistonD.

Lessening of atmospheric (or ambient) pressure expands the capsule H, thus raising valve F, reducing the pressure in C and therefore the resilient load on. valve A which consequently controls the pressure below: it to. a lowervalue. Meanwhile, piston D rises and the capsule H is consequently dropped, restoring valve F to an" equilibrium position. With increase of ambient pressure the converse action takes place. connection E is deemed tobe supplied: with servo fluid at constant pressure, and G may, conveniently, return servo fluid to a reservoir provided therefor.

The function of the valve deviceshown in Fig-- ure 2 is the same.

The valve device comprises a casing orbod y I having a relief-valve seat 2,, and relief valve 3 which is on a stem and spring-urged towards the. seat by a pack of springs 4 selected to give the required rate. The spring pack t is housed in a cylindrical chamber 4A and reacts on the under side of a! servo piston 5. sliding in a cylinder To. the underside of the. valve 3' is. supplied the, fuel entering the body I: under pressure by: the union 3A at the full pressure of the fuel pump. Fuel rising and passing thevalve 3V is collected in the spring chamber 4A and escapes through a union tito. return to. the-fuel source e. g, a tank.

The. load of the spring pack 4;. on the: valv 31isa determined by the position of the-piston. 5 Serve: fluid pressure acts. above this. piston in th space 1;, which communicates; by a duct 8: with a slide valve port; controlled by: a slide servo. valve 9: which either admits. servo. fluid (which. sup-5 plied through union H]: to thespace I or emits. it from thespace through union. It. The valve 9 is preferably so. dimensioned in relation to its. port that. when the valve is balanced it allows; a very small". now from H); to M", maintaining the. servopressure in space 1...

The valve 9 is. moved through. a stem STA bythe deformations: of a. flexible barometric: cap. sule I2: which is. evacuated; and acts as a pres-a. sure sensitive device. The ambientpressure-com-l municates with the interior of a chamber t3; through. a.- vent it; which is suitably protected: to. prevent. ingress of foreign. matter. The cap:

sul'e. L2 housed: inthe chamber. ll3,.is-.mounted; at.

its lower end on a. guided rod l5 which. isv en!- The " whole of the capsule l2.

gaged by the forked end I6A of a rocker l 6 home at IBB, the tail of which rocker is acted upon by a pushrod i'i slidable in structure of the body I, the upper end of the pushrod abutting against the underside of the piston 55. This push and rocker mechanism acts as a. follow-up device, because the position of the piston 5 determines the location of the capsule l2 within its chamber It, thus when an expansion of the capsule it causes valve 9 to rise, emitting servo-fluid from th space 'Lth piston 5 rises (by influence of the spring pack; Ll) thereby reducing the fuel pressure required to open the valve 3, and simultaneously the pushrod ll rises, dropping the This train of action corresponds with a fall in ambient pressure in 13,1. e.,, with an increase of altitude (or decrease of forward speed in a case Where pitot pressure is a factor). Its result in the fuel system is, to reduce the supply pressure for a given set of. conditions, thusto reduce the fuel supply to the engine. The body iis formed with jacket spaces as at A in which relieved fuel circulates to maintain the temperature of the working parts, especially theoylinder 5A.

A drain connection at It may-- be provided for any leakage of servo fluid, or condensate, which might otherwise accumulate in the chamber I3;

I claim:

1. A valve device for controlling the pressure of a first fluid flow in accordance with variations in pressure in a second fluid, comprising a resiliently loaded relief valve for adjusting the pressure of the first fluid, pressure fluid operated means for adjusting the resilient loading of said relief valve to any desired value over a range of values and a fluid pressure system of which the eifectiyepressure is controlled by variations inth pressure of the second fluidfor" operating said adjusting means, and abod 'y'contai-ningthe main operative parts of said device; said body having jacket spaces therein for the circulation of oneof said fluids for the purpose ofma-i ntain in-g required temperature conditions.

2. A valve device for controlling the pressure of a first iiuid flow in accordance with variations in pressure in a second fluid; comprising a resiliently loaded relief valve forad justing the pressure or the first fluid, a pressure fluid opera ati-ngr device having a cylinder with a piston therein separate from said relief valve but. directly engaging said resilient load of said relief valvefor adjusting the loading to any desired valueover a range of values and a fluid pressure system of which the effective pressure is con. trolled by: variationsin the pressure of the-second fluid for operating said adjusting piston.

3 A relief valve device for controlling the pres. sure of" a first fluidfiow. in accordance with variations. in the pressure in a. second fluid; comprise ing a relief valve with resiliently loading meansfor; loading it: towards its. closed: position servo system means includi-nga cylinder with a power piston separate from; said relief valve but directly engaging said resiliently: loadingmeans'. for load ing: it, servovalve means-for controlling-theload ing of: said: power piston to any desired value over a range: of values, a follow-up device nic chani'cally; linking said piston and said servo valve: means and apressure sensitivemeans in the linkage sensitive to.v.ariations.in the pressure offsaitl' second fluidfor varying; it.

DANIEL. NORMAN WALKER.

(References on. following: page) References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Marsh Dec. 17, 889 Bolton Feb. 1, 1921 McVay Apr. 5, 1927 Rode Apr. 1, 1930 Jenkins Aug, 19, 1930 Dodson Apr. 16, 1935 10 Johnson July 6, 1937 Number Number Name Date Halas Sept. 26, 1939 Saur Feb. 6, 1940 Huber Mar. 24, 1942 Temple May 19, 1942 Stieglitz Mar. 12, 1946 Warner Oct. 8, 1946 FOREIGN PATENTS Country Date Great Britain Jan. 26, 1939 

